Tell me about a time you aimed too low.

I have never been in sales, but the example answer I want to give is an example of answering the question while displaying good traits. Remember to be clear when explaining your experience and don't assume that they will understand everything. You should explain it step by step.

This is not a bad mistake. You can say you were burned out, or needed to take some time off, or wanted to rejuvenate yourself. This answer doesn't show a failure, but shows a great success. In this example, aiming too low resulted in great numbers and great results at the end of the month, so there is no harm done. In the end you are indicating that you could have done even better, that you are willing to re-evaluate your goals, and that you are now able to see and jump on opportunities.